Professor Andrew Bunker

Abstract:

James Webb Space Telescope (JWST) has revealed a population of ‘Little Red Dots’ (LRDs): compact, red objects at redshifts with ‘v’-shaped spectral energy distributions, broad permitted lines, and, often, hydrogen Balmer absorption. We use NIRSpec/IFS data from the BlackTHUNDER survey to study the H α line in the LRD Abell2744-QSO1 at , which is a confirmed active galactic nucleus (AGN) due to time-variable equivalent width (EW) in its broad emission lines. The H α spectral profile is non-Gaussian, requiring at least two Gaussian components. We also detect a narrow-line Gaussian component, and strong H α absorption (EW relative to the continuum ), confirming a connection between the strong Balmer break and line absorption. The absorber is at rest with respect to broad H α , suggesting that the gas cannot be interpreted as an inflow or outflow, forming instead a long-lived structure. Its velocity dispersion is , consistent with the value inferred from the analysis of the Balmer break. Based on H α , we infer a black hole mass of , smaller but close to the previous estimates based on H β . The Eddington ratio is 0.09. Combining the high signal-to-noise ratio of the narrow H α line with the spectral resolution of the G395H grating, we infer a narrow-line intrinsic dispersion , which places a stringent constraint on the black hole-to-dynamical mass ratio of this system to be , confirming the overmassive nature of the black hole and potentially leaving little room for a host galaxy.

Abstract:

We present the UV-to-near-IR (NIR) size evolution of a sample of 161 quiescent galaxies with M* > 1010 M⊙over 0.5 < z < 5. With deep multiband NIRCam images in GOODS-South from JADES, we measure the effective radii (Re) of the galaxies at rest-frame 0.3, 0.5, and 1 μm. On average, we find that quiescent galaxies are 45% (15%) more compact at rest-frame 1 μm than they are at 0.3 μm (0.5 μm). Regardless of wavelengths, the Re of quiescent galaxies strongly evolves with redshift, and this evolution depends on stellar mass. For lower-mass quiescent galaxies with M* = 1010–1010.6 M⊙, the evolution follows Re ∝ (1 + z)−1.1, whereas it becomes steeper, following Re ∝ (1 + z)−1.7, for higher-mass quiescent galaxies with M* > 1010.6 M⊙. To constrain the physical mechanisms driving the apparent size evolution, we study the relationship between Re and the formation redshift (zform) of quiescent galaxies. For lower-mass quiescent galaxies, this relationship is broadly consistent with Re∝(1+zform)−1 , in line with the expectation of the progenitor effect. For higher-mass quiescent galaxies, the relationship between Re and zform depends on stellar age. Older quiescent galaxies have a steeper relationship between Re and zform than that expected from the progenitor effect alone, suggesting that mergers and/or post-quenching continuous gas accretion drive additional size growth in very massive systems. We find that the z > 3 quiescent galaxies in our sample are very compact, with mass surface densities Σe ≳ 1010 M⊙ kpc−2, and their Re are possibly even smaller than anticipated from the size evolution measured for lower-redshift quiescent galaxies. Finally, we take a close look at the structure of GS-9209, one of the earliest confirmed massive quiescent galaxies at zspec ∼ 4.7. From UV to NIR, GS-9209 becomes increasingly compact, and its light profile becomes more spheroidal, showing that the color gradient is already present in this earliest massive quiescent galaxy.

Abstract:

We present JWST/NIRSpec IFU observations of the galaxy system B14-65666, as part of the GA-NIFS survey. Line and continuum emission in this massive system () is resolved into two strong cores surrounded by diffuse emission, as seen in recent JWST/NIRCam imaging. Our data set contains detections of [O ii], [Ne iii], Balmer lines, [O iii], He i, and weak [O iii]. Each spectrum is fit with a model that consistently incorporates interstellar medium conditions (i.e. electron temperature, , electron density, , and colour excess, ). The resulting line fluxes are used to constrain the gas-phase metallicity ( solar) and H-based star formation rate for each region. Common line ratio diagrams (O32–R23, R3–R2, Ne3O2–R23) reveal that each line-emitting region lies at the intersection of low- and high-redshift galaxies, suggesting low ionization and higher metallicity compared to the predominantly lower-mass galaxies studied with the JWST/NIRSpec IFU so far at . Spaxel-by-spaxel fits reveal evidence for both narrow (FWHM km s) and broad (FWHM km s) line emission, the latter of which likely represents tidal interaction or outflows. Comparison to ALMA [C ii]158m and [O iii]88 m data shows a similar velocity structure, and we explore optical-far infrared diagnostics. The two core galaxies both lie on the mass-metallicity relation at , but show contrasting properties (e.g. , ), suggesting distinct evolutionary pathways. Combining the NIRSpec IFU and ALMA data sets, our analysis opens new windows into the merging system B14-65666.

Abstract:

We present an overview of the James Webb Space Telescope (JWST) Advanced Deep Extragalactic Survey (JADES), an ambitious program of infrared imaging and spectroscopy in the GOODS-S and GOODS-N deep fields, designed to study galaxy evolution from high redshift to cosmic noon. JADES uses about 770 hr of Cycle 1 guaranteed time largely from the Near-Infrared Camera (NIRCam) and Near-Infrared Spectrograph (NIRSpec) instrument teams. In GOODS-S, in and around the Hubble Ultra Deep Field and Chandra Deep Field South, JADES produces a deep imaging region of ∼42 arcmin2 with over 100 hr of exposure time spread over nine NIRCam filters, including two medium-band filters. This is extended at medium depth in GOODS-S and GOODS-N with NIRCam imaging of ∼167 arcmin2, averaging 25 hr of exposure over 8–10 filters. In both fields, we conduct extensive NIRSpec multiobject spectroscopy, including two deep pointings of 55 hr exposure time, 14 medium pointings of ∼12 hr, and 15 shallower pointings of ∼4 hr, targeting over 5000 Hubble Space Telescope– and JWST-detected faint sources with five low-, medium-, and high-resolution dispersers covering 0.6–5.3 μm. Finally, JADES extends redward via coordinated parallels with the JWST Mid-Infrared Instrument, featuring ∼10 arcmin2 with 43 hr of exposure at 7.7 μm and thrice that area with 1.4–6.8 hr of exposure at 12.8 and 15 μm. For nearly 30 yr, the GOODS-S and GOODS-N fields have been developed as the premier deep fields on the sky; JADES is now providing a compelling start on JWST's legacy in these fields.